I think the format I suggested would parse in markdown, but I created it pre-markdown.
For me the best parts are:
1. You could write a parser very quickly.
2. It's very easy to edit and add to as a human.
3. It can easily be tracked in git or via a diff-based tool.
I did already think about the repetitive tasks, a long time ago I used to have a tool that would look at the past tasks and recommend future tasks (with appropriate distributions). One example was booking a dentist appointment every 6 months, even if I forgot to schedule something it would remind me to book one in, dismiss it or push it back.
I think my approach would be to generate a file in Markdown, then import that into a good Markdown editor. You could generate it each week or month from a template, making it easier to add repeating tasks like exercise and dog walking.